Smith has not played since Sept. 22 after he spent five weeks in a treatment center. He checked himself into rehab three days after he was arrested and jailed on suspicion of DUI and marijuana possession.

Fangio said he expects the All-Pro outside linebacker to play Sunday, but the number of snaps will depend on his conditioning level after a six-week layoff.

Smith had his first full practice since mid-September on Wednesday.

"He was a little rusty, obviously, from the six-week layoff," Fangio said. "But I expect him to get it back very quickly. He's not like a guy coming off an injury that he's got to overcome. He's just to overcome inactivity. You know, six weeks is a fairly long time, but not that long to where he can't get back into the swings of things pretty quickly."

The third-year pro combined for 33 1/2 sacks the past two seasons. This year, he had 4 1/2 sacks and 18 tackles in three games.

Smith is also facing three felony charges of possession of assault weapons filed by the Santa Clara County District Attorney on Oct. 9, stemming from a party at his home in June 2012.